Optimizing photoreceptor cell replacement therapies in human retinal pathology models: mechanisms of cell integration

光感受器(PR)细胞移植替代疗法是一种很有前途的治疗方法。临床前动物研究令人鼓舞，但许多基本问题仍然存在，为有效的临床翻译提供坚实的基础。一个关键的问题是能否开发出有效的细胞替代疗法来治疗遗传性视网膜营养不良和黄斑变性疾病，即哪些患者和病理阶段是最佳靶点。另一个关键挑战是，尽管有证据支持在小动物疾病模型中成功整合小鼠和人类PR并恢复一些视觉功能，但整合细胞的数量仍然很低。调节和限制细胞移植整合的机制仍不清楚，动物和人类之间可能有所不同。数据表明，宿主视网膜和细胞移植的特性都可能决定移植是否可以进入视网膜，在结构/功能上整合并在视网膜中存活。动物研究表明，视网膜变性，如疤痕和神经胶质病理，可能是细胞移植的物理障碍。因此，我们如何定义和如何刺激固有的细胞移植特性，以获得高整合能力和允许的宿主视网膜环境？为了帮助克服这些差距并促进临床翻译，人类实验系统可能是有用的。人类视网膜器官(HRO)技术使3D组织的产生成为可能，为基础研究和转化医学提供了新的视角。我们建立了一个高效而健壮的hPSC来源的HRO系统，并用它建立了一个可诱导的复杂的视网膜病理模型，包括视锥和视杆细胞的PR变性和神经胶质病理。从这个模型中，我们发现了新的发病机制，这导致了如何使用后者来优化移植整合的新假设。利用我们的HRO系统和病理模型，我们在第一个资助期建立了临床前人类细胞替代治疗研究平台，显示PR移植大量整合到HRO中，并伴随着晚期病理。在这里，我们将使用这个系统进行细胞移植的机制研究：操纵宿主HRO和移植，并优化PR结构和功能整合。我们的具体目标是：(1)确定PR移植整合是否与病理表型和分期有关。我们建立了几种不同表型的高脂血症新的病理模型。(2)调查已定义的PR属性是否提供主动入侵宿主视网膜的能力，或者PR是否被宿主视网膜摄取。(3)利用明确的视网膜病变机制来刺激PR移植整合。总之，拟议的项目旨在在临床前的人类环境中进行假设驱动的、可重复的、可量化的和机械性的研究，这可能会推动公关移植走向临床翻译。

Photoreceptor (PR) cell replacement therapy by cell transplantation represents a promising therapeutic approach. Preclinical animal studies are encouraging, but many fundamental questions still remain to provide a solid basis for effective clinical translation. A key question is whether effective cell replacement therapies can be developed for inherited retinal dystrophies and macular degenerative diseases, i.e. which patients and pathology stages are optimal targets. Another key challenge, although evidence support successful integration of mouse and human PRs and the restoration of some visual function in small animal disease models, the number of integrating cells is still low. The mechanisms regulating and limiting cell transplant integration are still unknown, and might differ between animals and human. Data indicate that the properties of the host retina and the cell transplant both might determine if transplants may enter, structurally/functionally integrate and survive in the retina. Animal studies suggest that retinal degeneration, e.g. scars and glial pathology, might be a physical barrier for cell transplants. Thus, what defines and how can we stimulate intrinsic cell transplant properties for high integration competence, and a permissive host retina environment? To help overcoming such gaps and to facilitate clinical translation, a human experimental system might be useful. Human retinal organoid (HRO) technology enables the generation of 3D tissues that offer new perspectives for fundamental research and translational medicine. We established an efficient and robust hiPSC–derived HRO system, and develop with it an inducible complex retinal pathology model with cone and rod PR degeneration and glial pathologies. From this model, we identified novel pathomechanisms, that led to new hypotheses how to use latter to optimize transplant integration. Using our HRO system and pathology model, we established a preclinical human cell replacement therapy research platform in the first funding period, showing that PR transplants integrate into HRO with late-stage pathology in high numbers. Here, we will use this system for mechanistic studies of cell transplantation: to manipulate host HRO and transplants, and to optimize PR structural and functional integration. Our specific aims are: (1) Determine if PR transplant integration is pathology phenotype- and stage-dependent. We established several novel pathology models with different phenotypes in HROs. (2) Investigate if defined PR properties provide competence to actively invade the host retina, or whether PRs are taken up by the host retina. (3) Utilize the function of defined retinal pathomechanisms to stimulate PRs transplant integration. Together, the proposed project aims to perform hypothesis-driven, reproducible, quantifiable and mechanistic studies in a preclinical human setting, that might advance PR transplantation towards clinical translation.